如何监控全局修饰键状态(在任何应用程序中)？

#include<Windows.h>

bool IsKeyPressed(int keyCode) {
    return (GetKeyState(keyCode) & 0x8000) != 0;
}

bool IsCapsLockOn() {
    return IsKeyPressed(VK_CAPITAL);
}

#import <Cocoa/Cocoa.h>
#import <CoreGraphics/CoreGraphics.h>

bool IsCapsLockOn() {
    CGEventSourceRef src = CGEventSourceCreate(kCGEventSourceStateHIDSystemState);
    CGEventRef evt = CGEventCreateKeyboardEvent(src, kVK_CapsLock, true);
    CGEventSetType(evt, kCGEventKeyDown);
    CGEventPost(kCGHIDEventTap, evt);
    CFRelease(evt);
    CFRelease(src);
    return true;
}

#include <X11/Xlib.h>
#include <X11/keysym.h>

bool IsCapsLockOn() {
    Display* display = XOpenDisplay(NULL);
    bool isCapsLockOn = false;
    if (display != NULL) {
        unsigned n;
        XkbGetIndicatorState(display, XkbUseCoreKbd, &n);
        isCapsLockOn = (n & 1) == 1;
        XCloseDisplay(display);
    }
    return isCapsLockOn;
}